Universal motor speed governor



May 9, 1939. s. H. SWARTHOUT 2,157,640

UNIVERSAL MOTOR SPEED GOVERNOR Filed June 23,.1958

NTOR

BY m 4- ATTORNEY/4 P atented May 9, 1939 UNITED STATES PATENT OFFICE toGeneral Motors Corporation,

Delaware a corporation of Application June 23,

3 Claims.

This invention relates to a universal electric motor, that is, a motorwhich will work either on alternating current or direct currentcircuits.

More particularly the invention relates to a speed 5 governor foruniversal electric motors.

The present invention is applicable to speed governors of the make andbreak contact type and is particularly useful on governors where thecontact separation or the wiping action of the contact is small. Underthese conditions and where close regulation of the speed is required itwill be seen that the space between the contacts must be maintained. Itis well known that on contacts interrupting a direct current circuit thepositive contact is liable to form a crater or pit and the negativecontact will in turn build up in the form of a cone or needle or othershape, this action being progressive. On contacts interrupting analternating current circuit, since the current is reversed every halfcycle, there is no chance for either contact to build up or pit andconsequently both contacts wear down evenly. The pitting of the onecontact and the building up on the other which ordinarily occurs withdirect current use may seriously affect the regulation of the motorspeed; therefore, it is very desirable to eliminate the transfer ofmaterial between the contacts to obtain uniform and equal wear on bothcontacts.

The object of the present invention is to provide means for obtaininguniform wear of the contacts on a speed governor or motor regardless ofwhether it is used on direct or alternating current.

Further objects and advantages of the present' invention will beapparent from the following description, reference being had to theaccompanying drawing wherein a preferred embodiment of the presentinvention is clearly shown.

The figure of the drawing is a wiring diagram embodying the presentinvention.

One application of the electric motor embodying the present invention isto drive a direct current generator for supplying current to the poweramplifier of a motion picture outfit which incorporates sound effects.As the motor circuit embodying the present invention is capable of otheruses the particular load which is applied to the motor is not shown inthe figure of the drawing.

In the drawing 23 designates a universal motor 30 of the series typehaving one of its brushes 2| connected with the series field winding 23which is connected with line wire 24. The motor armature shaft 2! drivesa disk 33 on one side of which are mounted two speed-responsive circuitbreak- 3 era 3| and 32, which are similar in construction.

Detroit, Mich.,

1938, Serial No. 215,426 (or. 171-312) Circuit breaker 3| comprises arelatively stationary contact 33 cooperating with a relatively movablecontact 34. Contact 33 is mounted on a plate 35 supported by leaf spring33 attached to a bracket 31, the disk 30. Contact 34 is attached to apair of plates 33 supported upon a leaf spring 33 attached to a bracket40 which is insulatingly supported by the disk 30. The plates 38serve asa weight which is affected by centrifugal force to cause it to moveoutwardly from the shaft 25 so as to separate the contact 34 from thecontact 33 at a predetermined speed. Spring 39 biases contact 34 intoclosed position. The speed at which contact 34 separates from contact 33is varied by varying the tension in spring 39 which is controlled by aset screw 4| mounted on'a bracket 42 insulatingly supported by the disk30.

The other circuit breaker 32 has contacts 43 and 44 corresponding,respectively, to contacts 33 and 34 of breaker 3|. The parts of thebreaker 32 supporting contacts 33 and 34 have been identifled byreference numbers which are the same as the reference numbers applied tothe corresponding parts of the breaker 3|, except that the letter a" isaffixed.

The contacts of the circuit breakers 3| and 32 are connected with acommutating device located on the reverse side of the disk 30. Thecommutating device comprises an outer split ring including the parts Kand L, a continuous collector ring N and a continuous collector ring U.The contacts 33 and 34 of breaker 3|, which will hereinafter be known ascontacts 0, are connected with the split connector rings K and L bywires 53 and 54 respectively. The contacts 43 and 44 of breaker 30,which will hereinafter be known as contacts P, are connected by wires 63and 64 respectively with continuous collector rings Q and N. The frameof the electric motor insulatingly supports brushes 13 and H which bearupon the half rings K and L, a brush 7". which bears on the ring N and abrush 13 which bears on the ring Q. The ring parts K, L, N and Q areinsulatingly supported by the disk 30. The ends of the ring parts K andL are provided with tungsten inserts T.

The brush i0 is connected by wire 14 with wire 15 which is connectedbetween brush 12 and motor commutator brush 22; brush 10 is alsoconnected by wire 13 with a resistor I which is connected by wire 11with line wire 23. A condenser H is in shunt with resistor 1. Brush 1|is connected by wire I3 with a contact D. Brush I3 is connected by wire13 with a contact E. The contacts D and E are parts of a relay whichinclude also a double which is insulatingly supported by 2 v contactmounted on an armature 80 pivoted at 8| and urgedin a clockwisedirection by a spring 82, one end of which isflxed with armature 80 andthe other'with a stationary part 83. The relay '5 1 includes anelectromagnet B, the winding of which 5 cuit: wire 24,

5 the speed is regulated by the contacts 0. when segment L, brush II,

is connected to line wire 26 and the other end of which is connectedthrough a condenser F to a line wire 24. It will be observed sincemagnet winding Bis connected only by capacity F with line wire 24 therelay will operate only on alternating-current applied tojthe; linewires 24 and 26.

When'direct current is applied to the wires 24 and 26 current flowsmotor field winding. 23, armature I5, wire 14 to the brush l0, brush II;wire 18,

come the bias of the spring 39, thereby causing 30 the contact 34 (ofthe pair of contacts 0) to be separated from the, contact 33. Sincethese contactsfO are in series with the electricmotor as previouslyexplained, theoperation of the motor will be aiiected by the opening ofthe contacts 0,

35 whereby the motor speed will decrease; and then,

when the speed has decreased to a certain value the contactsO will closeagain. In this way the speed is regulated by the speed-responsivecircuit breaker' 3|. The resistor I, which like the condenser H is inshunt to the contacts 0, is of a suitable value for preventing the motorcircuit from being interrupted when the contacts are open, while notaffecting the speed of regulation. The resistor I reduces sparking atthe contacts 0 and is assisted by the condenser H in this function.

direct current operation of the motor the description has been given asthough the commutating segments K and L were stationary. Obviously theirposition is reversed every half revolution of the motor shaft.Therefore, every half revolution thedirection of the currentnow throughthe contacts O is reversed. In this way the, transfer.

of material across the contacts in one direction is compensated for bypractically equal transfer, of

the material between the contacts in the opposite a direction. Then thetendency for. the contacts to;

build up or pit is practically eliminated. v

When alternating current is applied to theline wires 24 and 26 currentflows denser F and the relay armature is attracted toward the magnet andopens the circuit between C and'D and closes the circuit between-C andE. Therefore, the following circuit is operative during whichalternating current is applied to the wire: line wire 24, motorfleld'winding 22, armature of the motor,

wire-15, brush l2, commutating ring N, wire 84,,

70 contacts P wire 48; commutatlns r1118 Q, brush 1;, 1.

ll, contact E, contact-C, armature l0 and will then be seen that, whenwire line wire 24. It alternatin current 24 and 28, the continuousllector rings N and through the following cirlinewire "and Q must beused.

' speed governor weight 38 will over- In describing the circuits whichfunction during through the con ding B. Hence, the

is applied to the line wires.

contacts P'are used. These contacts P function to regulate the motorspeed when operating on alternating current in the same manner as thecontacts 0 function to regulate the motor speed when operating on directcurrent. The condenser H and the resistor I are also shunted across thecontacts P through the Q and the governor following circuit: wire 16,brush 10, wire 14, wire I5, brush 12, collector ring, N, wire 64,contacts P, wire 63, ring Q, brush 13, wire 19, contact E, contact C,armature 80, wire 26 and wire I1 back to the condenser H and resistor I.The condenser H and resistor I function to reduce sparking at thecontacts E.

It has been found that, in order to obtain the desired operating lifefrom the governor, the split collector rings K and L can not be used foralternating current operation on a volt circult and that the continuouscollector rings N It is apparent from the foregoing description of theconstruction and mode of operation'of the governor circuits, embodied inthe present invention, that there has been provided a motor with a inwhich very close speed regulation can be obtained and maintained overlong periods of operation regardless of whether the motor is operatedupon alternating or direct cur- I rent.

While the embodiment of the present invention as herein disclosed,constitutes a preferred form, it is to be understood that otherforms-might be adopted, all coming within the scope of the claims whichfollow.

What is claimed is as follows:

1.- A control circuit for universal motors comprising, in combination,two speed responsive circuit breakers driven by the motor, means forautomatically selectively connecting one or the other of said circuitbreakers in circuit with the motor depending on whether the motoroperates on direct current 01 on alternating current, whereby the motorspeed will be regulated when the motor operates on either kind ofcurrent, and means for automatically reversing polarity through thecontacts of that speed responsive circuit breaker which regulates thespeed of the motor when operating on direct current.

2. A control circuit according to claim 1 in which the automaticselecting means comprises an electromagnet relay having anarmature'normally biased tocomplete the circuit of the electric motorthrough the circuit breaker which controls motor speed for directcurrent operation and having an electro-magnet winding capacity-coupledacross the line so as to be energized by alternating current only, theenergizing of the electromagnet by alternating current causing thearmature to disconnect the D. C. circuit breaker for controlling speed,and to connect the A. C. circuit breaker for controlling speed. 4 f N,3. A control circuit according. to claim 1 in which the means forautomatically reversing polarity through the contacts of the speedresponsive circuit breaker which regulates motor speed when operating ondirect current comprises a motor-driven bi-segmental, split collectorring having its segments connected respectively with said contacts andmounted, and brushes cooperating with the split ring for connecting thesegments with the motor and line, the polarity through the segmentsbeing automatically reversed by the motor.

STANLEY H. SWARTHOUT.

